Add fallback parsing support for single-file apphost projects

src/Aspire.Cli/Projects/FallbackProjectParser.cs

@@ -3,97 +3,160 @@
 
 using System.Text.Json;
 using System.Text.Json.Nodes;
+using System.Text.RegularExpressions;
 using System.Xml.Linq;
 using Microsoft.Extensions.Logging;
 
 namespace Aspire.Cli.Projects;
 
 /// <summary>
-/// Provides fallback XML parsing capabilities when MSBuild evaluation fails.
+/// Provides fallback parsing capabilities when MSBuild evaluation fails.
+/// Supports both .csproj XML files and .cs single-file apphost files.
 /// Used primarily for AppHost projects with unresolvable SDK versions.
 /// </summary>
-internal sealed class FallbackProjectParser
+internal sealed partial class FallbackProjectParser
 {
     private readonly ILogger<FallbackProjectParser> _logger;
 
+    [GeneratedRegex(@"#:sdk\s+Aspire\.AppHost\.Sdk@([\d\.\-a-zA-Z]+|\*)")]
+    private static partial Regex SdkDirectiveRegex();
+
+    [GeneratedRegex(@"#:package\s+([a-zA-Z0-9\._]+)@([\d\.\-a-zA-Z]+|\*)")]
+    private static partial Regex PackageDirectiveRegex();
+
     public FallbackProjectParser(ILogger<FallbackProjectParser> logger)
     {
         _logger = logger;
     }
 
     /// <summary>
-    /// Parses a project file using direct XML parsing to extract basic project information.
+    /// Parses a project file using direct parsing to extract basic project information.
     /// Returns a synthetic JsonDocument that mimics MSBuild's GetProjectItemsAndProperties output.
+    /// Supports both .csproj XML files and .cs single-file apphost files.
     /// </summary>
     public JsonDocument ParseProject(FileInfo projectFile)
     {
         try
         {
-            _logger.LogDebug("Parsing project file '{ProjectFile}' using fallback XML parser", projectFile.FullName);
-
-            var doc = XDocument.Load(projectFile.FullName);
-            var root = doc.Root;
+            _logger.LogDebug("Parsing project file '{ProjectFile}' using fallback parser", projectFile.FullName);
 
-            if (root?.Name.LocalName != "Project")
+            // Detect file type and route to appropriate parser
+            if (string.Equals(projectFile.Extension, ".csproj", StringComparison.OrdinalIgnoreCase))
             {
-                throw new InvalidOperationException($"Invalid project file format: {projectFile.FullName}");
+                return ParseCsprojProjectFile(projectFile);
             }
-
-            // Extract SDK information
-            var aspireHostingSdkVersion = ExtractAspireHostingSdkVersion(root);
-
-            // Extract package references
-            var packageReferences = ExtractPackageReferences(root);
-
-            // Extract project references
-            var projectReferences = ExtractProjectReferences(root, projectFile);
-
-            // Build the synthetic JSON structure using JsonObject
-            var rootObject = new JsonObject();
-
-            // Items section
-            var itemsObject = new JsonObject();
-
-            // PackageReference items
-            var packageRefArray = new JsonArray();
-            foreach (var pkg in packageReferences)
+            else if (string.Equals(projectFile.Extension, ".cs", StringComparison.OrdinalIgnoreCase))
             {
-                var packageObj = new JsonObject();
-                packageObj["Identity"] = JsonValue.Create(pkg.Identity);
-                packageObj["Version"] = JsonValue.Create(pkg.Version);
-                packageRefArray.Add((JsonNode?)packageObj);
+                return ParseCsAppHostFile(projectFile);
             }
-            itemsObject["PackageReference"] = packageRefArray;
-
-            // ProjectReference items
-            var projectRefArray = new JsonArray();
-            foreach (var proj in projectReferences)
+            else
             {
-                var projectObj = new JsonObject();
-                projectObj["Identity"] = JsonValue.Create(proj.Identity);
-                projectObj["FullPath"] = JsonValue.Create(proj.FullPath);
-                projectRefArray.Add((JsonNode?)projectObj);
+                throw new ProjectUpdaterException($"Unsupported project file type: {projectFile.Extension}. Expected .csproj or .cs file.");
             }
-            itemsObject["ProjectReference"] = projectRefArray;
-
-            rootObject["Items"] = itemsObject;
-
-            // Properties section
-            var propertiesObject = new JsonObject();
-            propertiesObject["AspireHostingSDKVersion"] = JsonValue.Create(aspireHostingSdkVersion);
-            rootObject["Properties"] = propertiesObject;
-
-            // Fallback flag
-            rootObject["Fallback"] = JsonValue.Create(true);
-
-            // Convert JsonObject to JsonDocument
-            return JsonDocument.Parse(rootObject.ToJsonString());
+        }
+        catch (ProjectUpdaterException)
+        {
+            // Re-throw our custom exceptions
+            throw;
         }
         catch (Exception ex)
         {
-            _logger.LogError(ex, "Failed to parse project file '{ProjectFile}' using fallback XML parser", projectFile.FullName);
-            throw new ProjectUpdaterException($"Failed to parse project file '{projectFile.FullName}' using fallback XML parser: {ex.Message}", ex);
+            _logger.LogError(ex, "Failed to parse project file '{ProjectFile}' using fallback parser", projectFile.FullName);
+            throw new ProjectUpdaterException($"Failed to parse project file '{projectFile.FullName}' using fallback parser: {ex.Message}", ex);
+        }
+    }
+
+    /// <summary>
+    /// Parses a .csproj XML project file to extract SDK and package information.
+    /// </summary>
+    private static JsonDocument ParseCsprojProjectFile(FileInfo projectFile)
+    {
+        var doc = XDocument.Load(projectFile.FullName);
+        var root = doc.Root;
+
+        if (root?.Name.LocalName != "Project")
+        {
+            throw new InvalidOperationException($"Invalid project file format: {projectFile.FullName}");
         }
+
+        // Extract SDK information
+        var aspireHostingSdkVersion = ExtractAspireHostingSdkVersion(root);
+
+        // Extract package references
+        var packageReferences = ExtractPackageReferences(root);
+
+        // Extract project references
+        var projectReferences = ExtractProjectReferences(root, projectFile);
+
+        return BuildJsonDocument(aspireHostingSdkVersion, packageReferences, projectReferences);
+    }
+
+    /// <summary>
+    /// Parses a .cs single-file apphost to extract SDK and package information from directives.
+    /// </summary>
+    private static JsonDocument ParseCsAppHostFile(FileInfo projectFile)
+    {
+        var fileContent = File.ReadAllText(projectFile.FullName);
+
+        // Extract SDK version from #:sdk directive
+        var aspireHostingSdkVersion = ExtractSdkVersionFromDirective(fileContent);
+
+        // Extract package references from #:package directives
+        var packageReferences = ExtractPackageReferencesFromDirectives(fileContent);
+
+        // Single-file apphost projects don't have project references
+        var projectReferences = Array.Empty<ProjectReferenceInfo>();
+
+        return BuildJsonDocument(aspireHostingSdkVersion, packageReferences, projectReferences);
+    }
+
+    /// <summary>
+    /// Builds a synthetic JsonDocument from extracted project information.
+    /// </summary>
+    private static JsonDocument BuildJsonDocument(
+        string? aspireHostingSdkVersion,
+        PackageReferenceInfo[] packageReferences,
+        ProjectReferenceInfo[] projectReferences)
+    {
+        var rootObject = new JsonObject();
+
+        // Items section
+        var itemsObject = new JsonObject();
+
+        // PackageReference items
+        var packageRefArray = new JsonArray();
+        foreach (var pkg in packageReferences)
+        {
+            var packageObj = new JsonObject();
+            packageObj["Identity"] = JsonValue.Create(pkg.Identity);
+            packageObj["Version"] = JsonValue.Create(pkg.Version);
+            packageRefArray.Add((JsonNode?)packageObj);
+        }
+        itemsObject["PackageReference"] = packageRefArray;
+
+        // ProjectReference items
+        var projectRefArray = new JsonArray();
+        foreach (var proj in projectReferences)
+        {
+            var projectObj = new JsonObject();
+            projectObj["Identity"] = JsonValue.Create(proj.Identity);
+            projectObj["FullPath"] = JsonValue.Create(proj.FullPath);
+            projectRefArray.Add((JsonNode?)projectObj);
+        }
+        itemsObject["ProjectReference"] = projectRefArray;
+
+        rootObject["Items"] = itemsObject;
+
+        // Properties section
+        var propertiesObject = new JsonObject();
+        propertiesObject["AspireHostingSDKVersion"] = JsonValue.Create(aspireHostingSdkVersion);
+        rootObject["Properties"] = propertiesObject;
+
+        // Fallback flag
+        rootObject["Fallback"] = JsonValue.Create(true);
+
+        // Convert JsonObject to JsonDocument
+        return JsonDocument.Parse(rootObject.ToJsonString());
     }
 
     private static string? ExtractAspireHostingSdkVersion(XElement projectRoot)
@@ -172,6 +235,51 @@ private static ProjectReferenceInfo[] ExtractProjectReferences(XElement projectR
 
         return projectReferences.ToArray();
     }
+
+    /// <summary>
+    /// Extracts the Aspire.AppHost.Sdk version from the #:sdk directive in a single-file apphost.
+    /// </summary>
+    private static string? ExtractSdkVersionFromDirective(string fileContent)
+    {
+        // Match: #:sdk Aspire.AppHost.Sdk@<version>
+        // Where version can be a semantic version or wildcard (*)
+        var match = SdkDirectiveRegex().Match(fileContent);
+
+        if (match.Success)
+        {
+            return match.Groups[1].Value;
+        }
+
+        return null;
+    }
+
+    /// <summary>
+    /// Extracts package references from #:package directives in a single-file apphost.
+    /// </summary>
+    private static PackageReferenceInfo[] ExtractPackageReferencesFromDirectives(string fileContent)
+    {
+        var packageReferences = new List<PackageReferenceInfo>();
+
+        // Match: #:package <PackageId>@<version>
+        // Where version can be a semantic version or wildcard (*)
+        var matches = PackageDirectiveRegex().Matches(fileContent);
+
+        foreach (Match match in matches)
+        {
+            var identity = match.Groups[1].Value;
+            var version = match.Groups[2].Value;
+
+            var packageRef = new PackageReferenceInfo
+            {
+                Identity = identity,
+                Version = version
+            };
+
+            packageReferences.Add(packageRef);
+        }
+
+        return packageReferences.ToArray();
+    }
 }
 
 internal record PackageReferenceInfo

src/Aspire.Cli/Projects/ProjectUpdater.cs

@@ -63,10 +63,10 @@ public async Task<ProjectUpdateResult> UpdateProjectAsync(FileInfo projectFile,
             interactionService.DisplayEmptyLine();
         }
 
-        // Display warning if fallback XML parsing was used
+        // Display warning if fallback parsing was used
         if (fallbackUsed)
         {
-            interactionService.DisplayMessage("warning", "[yellow]Note: Update plan generated using fallback XML parsing due to unresolvable AppHost SDK. Dependency analysis may have reduced accuracy.[/]");
+            interactionService.DisplayMessage("warning", $"[yellow]{UpdateCommandStrings.FallbackParsingWarning}[/]");
             interactionService.DisplayEmptyLine();
         }
 
@@ -157,7 +157,7 @@ private static bool IsGlobalNuGetConfig(string path)
             await analyzeStep.Callback();
         }
 
-        return (context.UpdateSteps, context.FallbackXmlParsing);
+        return (context.UpdateSteps, context.FallbackParsing);
     }
 
     private const string ItemsAndPropertiesCacheKeyPrefix = "ItemsAndProperties";
@@ -202,12 +202,12 @@ private async Task<JsonDocument> GetItemsAndPropertiesWithFallbackAsync(FileInfo
         catch (ProjectUpdaterException ex) when (IsAppHostProject(projectFile, context))
         {
             // Only use fallback for AppHost projects
-            logger.LogWarning("Falling back to XML parsing for '{ProjectFile}'. Reason: {Message}", projectFile.FullName, ex.Message);
+            logger.LogWarning("Falling back to parsing for '{ProjectFile}'. Reason: {Message}", projectFile.FullName, ex.Message);
 
-            if (!context.FallbackXmlParsing)
+            if (!context.FallbackParsing)
             {
-                context.FallbackXmlParsing = true;
-                logger.LogWarning("Update plan will be generated using fallback XML parsing; dependency accuracy may be reduced.");
+                context.FallbackParsing = true;
+                logger.LogWarning("Update plan will be generated using fallback parsing; dependency accuracy may be reduced.");
             }
 
             return fallbackParser.ParseProject(projectFile);
@@ -863,7 +863,7 @@ internal sealed class UpdateContext(FileInfo appHostProjectFile, PackageChannel
     public ConcurrentQueue<UpdateStep> UpdateSteps { get; } = new();
     public ConcurrentQueue<AnalyzeStep> AnalyzeSteps { get; } = new();
     public HashSet<string> VisitedProjects { get; } = new();
-    public bool FallbackXmlParsing { get; set; }
+    public bool FallbackParsing { get; set; }
 }
 
 internal abstract record UpdateStep(string Description, Func<Task> Callback)

src/Aspire.Cli/Resources/UpdateCommandStrings.resx

@@ -111,4 +111,7 @@
   <data name="MappingRetainedFormat" xml:space="preserve">
     <value>   Mapping: {0}</value>
   </data>
+  <data name="FallbackParsingWarning" xml:space="preserve">
+    <value>Note: Update plan generated using fallback parsing due to unresolvable AppHost SDK. Dependency analysis may have reduced accuracy.</value>
+  </data>
 </root>